(1) Field of the Invention
The present invention relates to a capless writing instrument, in particular relates to a capless writing instrument having an anti-dryout mechanism.
(2) Description of the Prior Art
Conventionally, writing instruments, such as water-based and oil-based marker pens and water-based ball-point pens and fountain pens, are generally provided with a cap for sealing the tip part, in order to prevent the writing instrument from becoming unable to write due to dryout of ink at the tip of the writing element.
In the case of a writing instrument having a sealing cap for its writing point, it is necessary to remove and attach the cap every time the pen is used and this work bothers the user if the pen is used frequently. This is why many types of so-called capless writing instruments, which do not need to have a separate cap, have been proposed.
However, such capless writing instruments, in place of a cap, need to have a sealing mechanism for sealing the front-end part, in the narrow hollow interior of the writing instrument body, but such sealing mechanisms of conventional configurations are all complicated, needing many components, this results in complexity in assembly and increase in production cost.
As countermeasures against the above problem, as a sealing method of the writing tip, Japanese Utility Model Application Laid-Open Sho 49 No.32731(which will be called prior art example 1, hereinbelow) discloses a configuration in which a valve plate having cuts formed radially outwardly from the center therein is arranged at the front-end part inside the barrel cylinder of the writing instrument so that the writing tip can be projected through the cuts. Japanese Utility Model Application Laid-Open Hei 49 No.107421(which will be called prior art example 2, hereinbelow) discloses another configuration in which packings are arranged at the rear and front ends inside the barrel cylinder of the writing instrument so that the barrel cylinder interior can be sealed and the writing tip can be projected out through the front end packing against which the tip is abutted. Still another disclosure is proposed in Japanese Utility Model Application Laid-Open Sho 63 No.23084(which will be called prior art example 3, hereinbelow), in which an elastic self-closing element having an opening is provided at the front part of a cap body so that the writing point of the barrel cylinder front end can projected out.
There are still other methods. Japanese Patent Application Laid-Open Hei 1 No.281999(which will be called prior art example 4, hereinbelow) discloses a configuration in which a sealing means is provided at the front end inside the barrel cylinder of a writing instrument so as to open and close the front end side of the sealed compartment in which the writing point of the writing element is held and the front end side of the sealed compartment is opened when the writing point is projected from the front end. Japanese Utility Model Application Laid-Open Sho 58 No.89394(which will be called prior art example 5, hereinbelow) discloses a method in which a sealing structure for sealing the writing point is hermetically fitted at the front-end part of the front barrel at the front end inside the barrel cylinder of the writing instrument so that it opens and closes the front part of the fixed sealing structure as the front barrel moves.
However, according to the above prior art examples 1, 2 and 3, since openings have been formed from the beginning at their sealing portions through which the pen tip is projected, any of these configurations has a sealability problem before use.
On the other hand, the method described in the prior art example 4 has the problem that the arrangement of the sealed compartment, seal opening and closing mechanism and the like becomes complicated. Similarly, the arrangement described in the prior art example 5 needs to have separate parts for the sealing enclosure with an opening mechanism, hence cannot avoid its becoming complicated.
The present invention has been devised in view of the above conventional problems and it is therefore an object of the present invention to provide a capless writing instrument with a simple structure which can seal the writing point inside the barrel cylinder and assures the sealability of the writing point before use.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the first aspect of the present invention, a capless writing instrument, wherein a writing element is arranged in the barrel cylinder so that a writing point of the writing element can come out and retract through a front-end opening of the barrel cylinder, is characterized in that an inner cap formed of rubber or elastic resin is arranged at the front-end opening of the barrel cylinder and is formed with a strip-like thin-film portion that intersects the approximate center of the inner cap with respect to its axial direction, and the strip-like thin-film portion is broken forming a slit when the writing point is projected outside for the first time through the front-end opening of the barrel cylinder.
In accordance with the second aspect of the present invention, the capless writing instrument having the above first feature is characterized in that the strip-like thin-film portion is 0.01 to 1.0 mm wide and has a film thickness of 0.01 to 0.5 mm.
In accordance with the third aspect of the present invention, the capless writing instrument having the above first feature is characterized in that the inner cap is formed of sponge-like elastic material.
In accordance with the fourth aspect of the present invention, the capless writing instrument having the above second feature is characterized in that the inner cap is formed of sponge-like elastic material.
According to the present invention, the following effects can be obtained.
That is, according to the capless writing instrument of the present invention, since an inner cap formed of rubber or elastic resin is arranged at the front-end opening of the barrel cylinder, it is possible to keep the interior of the barrel cylinder sealed. Further, since the inner cap is formed with a strip-like thin-film portion that intersects the approximate center of the inner cap with respect to its axial direction, it is possible to assure the sealed state inside the barrel cylinder, over a prolonged period of time until it is used for the first time by projecting the writing point out.
Further, since the strip-like thin-film portion is broken so as to form a slit when the writing point is projected outside through the front-end opening of the barrel cylinder for the first time, it is possible to easily project the writing point through the slit. Since the inner cap is formed of rubber or elastic resin, the slit can be easily narrowed and kept in contact by virtue of the resiliency of the rubber or elastic resin, so that the sealed state can be re-established.
Since the strip-like thin-film portion is adapted to be 0.01 to 1.0 mm wide and have a film thickness of 0.01 to 0.5 mm, it is possible for the writing point to easily break the slit-forming groove without failure when the capless writing instrument is used for the first time. It is also possible to keep the opening of the slit closed in contact, hence maintain the sealed state of the interior of the barrel cylinder when it is not used even after breakage of thin-film portion.
Forming the inner cap of sponge-like elastic material enables easier and enhanced sealing of the interior of barrel cylinder.